A Surfside town inspector reportedly told residents of Champlain Towers South in 2018 that their building was safe despite an engineer’s warning of major damage a month before. The cause of Thursday’s deadly collapse is still unknown, but according to the engineering report, the structural slab was deteriorating because it was flat instead of sloped, meaning water didn’t drain but instead pooled on the concrete until it evaporated. The repairs to fix the issue would have been “extremely expensive,” but the report cautioned that it would “cause the extent of the concrete deterioration to expand exponentially” if it didn’t get fixed.

The report was dated Oct. 8, 2018. According to minutes from a Nov. 15 board meeting obtained by NPR, residents were told: “it appears the building is in very good shape.” Miami-Dade County Mayor Daniella Levine Cava told reporters that officials “knew nothing” about the report.